The Serial Peripheral Interface (SPI) is a conventional high speed synchronous serial input/output port that allows a serial bit stream of programmed length (2 to 16 bits) to be shifted into and out of devices at a programmed bit-transfer rate. The SPI is normally used for communication between a host device and external peripherals. Typical applications of SPI include interface(s) to external I/O or peripheral expansion via devices such as shift registers, display drivers, SPI Erasable Programmable Read-Only Memory (EPROMs) and analog-to-digital converters.
The figures are not to scale. Wherever appropriate, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts.